The invention relates to a fluid rotary passage for sealing a fluid pressure chamber between a rotatable shaft and a shaft seat, wherein the fluid rotary passage comprises a sealing ring carrier and a fitting body, wherein the sealing ring carrier is rotationally fixed to the shaft or to the seat in a fluid-tight manner and the fitting body is in contact with the other component in a fluid-tight manner, wherein the fitting body and the sealing ring carrier are radially spaced from each other, at least in sections, in order to create a fluid pressure chamber between them, and wherein two sealing rings are provided which are axially spaced from each other and which are each sealingly applied against the sealing ring carrier with one contact surface and which are sealingly applied against the fitting body with one contact surface, for sealing the fluid pressure chamber against the outside, and which can each be twisted, preferably independently from each other, with respect to the sealing ring carrier and/or to the fitting body,
Fluid rotary passages of this kind are used in various applications such as transmissions, in which the shaft is arranged in a rotatable manner with respect to the shaft seat, wherein a fluid pressure chamber is formed between the shaft and the shaft seat. In most cases, the rotatable shaft is constructed as a hollow shaft whose hollow space constitutes a fluid passage channel. The fluid passage channel of the shaft can be connected to the fluid pressure chamber in such a manner that a fluid can pass through. Also the shaft seat is often constructed as a hollow shaft and thus can also include a fluid passage channel that can be connected to the fluid pressure chamber in such a manner that a fluid can pass through. The fluid in the fluid pressure chamber between the shaft and the shaft seat is mostly pressurized. While oil such as hydraulic oil is frequently used as a fluid, air or a different gas can be used as well. The following embodiments can be used with any suitable fluid such as oil or air.
In fluid rotary passages of like kind, a sealing ring carrier is rotationally fixed to the shaft or to the shaft seat in a fluid-tight manner, and a fitting body is in contact with the respective other component of the shaft and the seat in a fluid-tight manner. The fitting body and the sealing ring carrier are radially spaced from each other, at least in sections, and form between them the fluid pressure chamber between the shaft and the shaft seat. The fluid pressure chamber is sealed against the outside via sealing rings, wherein the sealing rings are axially spaced from each other and are in sealing contact with the sealing ring carrier and the fitting body respectively via a contact surface thereof. The sealing rings are twistable with respect to the sealing ring carrier and/or the fitting body.
Accordingly, fluid rotary passages of like kind are constructed as a sealing arrangement, which comprises the elements: fitting body, sealing ring carrier, and sealing rings. The sealing arrangement can also comprise the shaft and/or the shaft seat. In fluid rotary passages of like kind, high relative rotational speeds can be implemented between the shaft and the shaft seat because the entire relative rotational movement is received by the sealing rings, whereas the sealing ring carrier and mostly also the fitting body are fixed for rotation with the shaft or the shaft seat. This particularly guarantees a reduction of friction losses in the fluid rotary passage and thus a prevention of a high temperature increase at high relative rotational speeds. Accordingly, in fluid rotary passages of like kind, relative twisting between the shaft and the shaft seat is enabled by a relative rotation of the fitting body and/or the sealing ring carrier with respect to the sealing rings. However, minor slippage of the fitting body and possibly also of the sealing ring carrier relative to the respective supporting component, i.e. the shaft or the shaft seat may however also occur during relative rotational movements.
Therefore, the co-action of the sealing rings with the fitting body or the sealing ring carrier in the fluid rotary passage is particularly important. The sealing rings are mostly made from a synthetic material and can be cut through at one circumferential position. The sealing rings have surfaces by which they can form at least one contact surface with the sealing ring carrier and the fitting body. In fluid rotary passages of like kind, the sealing ring carrier can be constructed, for example, as a sheet metal forming part in the manner of a double-collar bushing press-fitted to the shaft. However, the sealing ring can also be integrally formed with the shaft and particularly the sealing ring carrier can be a texture milled into the shaft. The fitting body can be formed, for example, as an injection-molded part from a high-strength synthetic material.
In fluid rotary passages of like kind, the sealing rings, the sealing ring carriers and the fitting body require a construction which guarantees preferably perfect sealing of the fluid pressure chamber against the outside through the contact surfaces of the sealing rings with the fitting body or with the sealing ring carrier on the one hand and lowest possible friction losses between the sealing rings and the fitting body or the sealing ring carrier on the other hand. In conventional fluid rotary passages this is achieved by the sealing rings being in contact with the sealing ring carrier or with the fitting body exclusively via their contact surfaces. However, various problems occur in this case.
For example, the assembly of conventional fluid rotary passages is difficult and it must be taken into account that during the assembly the shaft is introduced into the hollow shaft, with the sealing ring carrier, the fitting body and the sealing rings disposed between the hollow shaft and the shaft. For preventing friction in the assembled fluid rotary passage, the sealing rings are loosely arranged between the sealing ring carrier and the fitting body, while precisely the mounting of the sealing ring, for example, its fixation by inserting or clamping the sealing ring into a groove, is avoided. Accordingly, the sealing rings can be placed in a predetermined position only with difficulty. In addition, the fixation of the sealing rings at least is not possible as long as the fluid pressure chamber is not filled with pressurized fluid. This complicates the assembly of the fluid rotary passage on the one hand and may cause malfunction such as leakage in the assembled fluid rotary passage as a result of faulty positioning of the sealing ring on the other hand.
In fluid rotary passages of like kind it turned out that particularly the sealing rings frequently lack sufficient inherent rigidity, which makes installation much more difficult. Further, in fluid rotary passages of like kind, the sealing rings frequently tend to twisting as a result of being insufficiently guided in the fluid rotary passages, particularly prior to the presence of a pressurized fluid in the fluid pressure chamber.
In fluid rotary passages of like kind, sealing rings find their sealing position provided in the fluid rotary passage only behind time and/or insufficiently. This may lead to malfunction such as considerable leakage of the fluid rotary passages on the one hand. On the other hand, the response can be insufficient, particularly at a low fluid pressure of the fluid and/or at low relative rotation speeds of the shaft with respect to the shaft seat. This can be the case, for example, at a low rotation speed of the shaft relative to the shaft seat if the shaft is driven for example by a motor at its idling speed. For example, it is possible for a sealing ring to vary its position in the fluid rotary passage as long as the sealing ring is not arranged in its predetermined sealing position. As a result, the sealing ring can wear out and/or leak.
Further, conventional fluid rotary passages involve the problem of constructing the contact surfaces between the sealing rings and the sealing ring carriers or the fitting bodies in such a manner that reliable sealing is achieved while leakage and simultaneously the drag moment are as small as possible. No satisfying solution of this problem has been found up to present so that conventional fluid rotary passages either achieve low friction at the cost of a considerable leakage or very good sealing at the cost of high friction.